Engineering studies for me is pretty difficult, but it has given me a possibility that I could do Engineering as a career if my primary goal doesn't work out. It has stacks of content, and some of it does overlap with Physics, Maths and Chemistry. If you can handle all the content you need to learn and understand, it's not a *bad* subject, but it has definitely been a challenge so far. The reason I chose it was because nothing else in the line interested me, and as I got into it, it's very mathematical, which is up my alley.
You also need to consider your own interests. If you already have subjects like Physics, Maths (possibly Ext 1) and Chemistry, then that's enough for uni (it's not necessary to do Engineering Studies) and something else on the same line interests you, then I personally think you should take that. For me, I had to choose between Music and Chemistry, and I have never regretted this decision and may do better in my HSC as a result, because although Chemistry is good for a B. Science, it's not essential coz I'm doing Physics and MX1 too, plus Music, something I'm passionate about.
Choosing a HSC subject for your career isn't always the best way, follow your interests. But if that's Engineering Studies, go for it. Just make sure you commit to lots and lots of study for it, as there's a lot to know!!!
Hope this helps
~ Samii xx